13.1 The Challenge of Interstellar
Why is interstellar travel so difficult?
The large distances between stars, the speed of light being the fastest speed,
and enormous amount of energy required to accelerate any ship to high speed
are three difficulties with interstellar space.
Spacecraft bound for the stars
At current speeds it takes 100,000 years to reach the closest stars.
The pioneer carries a plaque
The voyager carries a gold-coated copper record
The cosmic speed limit
According to Einstein’s Theory of relativity it is not possible to travel at or faster
than the speed of light.
The energy required to accelerate an interstellar spaceship depends on its mass
and final velocity (mv )
The energy required to accelerate that Titanic to 10% of speed of light, will
require 100X the Earth’s annual energy usage.
Could we travel to star with existing rockets?
Development of the rocket
Chemical rockets work on the principle of Newton’s third law of motion
Chemical rockets are the most common type of spacecraft
The rocket equation relates final velocity to velocity of exhaust gases and ratio of the
mass of rocket with all its fuel to mass of rocket after fuel has been consumed
The mass ratio of a rocket is define by mass of fully fueled rocket divided by mass of
the rocket after fuel is burned
The earths escape velocity is the minimum velocity required for an object to escape the
A mass ratio of 39 is required to leave Earth’s gravity
In order to get payload into space, we must use multiple rocket stages
The maximum terminal velocity we can accelerate a chemical rocket is 0.1% speed of
light. 13.2 Designing Spacecraft for Interstellar Travel
How might we build interstellar spacecraft with “conventional”
Nuclear FIZZION is the process in which large nuclei break up into smaller nuclei
o It is more human so only 0.07% efficient
Nuclear FUSEion is the process in which smaller nuclei combine to form larger
The resultant helium is less massive than original four because energy is lost
o It is natural so 0.7% efficient
The maximum speed we can accelerate a nuclear rocket is 10% speed of light.
Project Rover in 1950’s developed nuclear fission reactors for rockets.
Project Orion in Los Alamos developed design for ship powered by H-bombs
Project Daedalus designed by British Interplanetary Society in 1970 was
propelled by nuclear fusion reactors.